Sunday, June 23, 2024 Convective Thread

[weatherwiz]

1 minute ago, WxWatcher007 said:

18z NAM has activity up in NNE around 12z tomorrow. Those soundings tomorrow from Albany to HFD look messy but legit. 

Shear is certainly there. Definitely some messy looks. One of the several reasons we won't see widespread, high-end severe and why we'll see probably one or two concentrated swaths of some severe. 

[WxWatcher007]

3 minutes ago, weatherwiz said:

Shear is certainly there. Definitely some messy looks. One of the several reasons we won't see widespread, high-end severe and why we'll see probably one or two concentrated swaths of some severe. 

One of my concerns (down in CT) is that we don’t see the discrete cell tornado risk, but rather cells in NY that congeal and bring a straight line risk. 

[Prismshine Productions]

Wow this is a substantial increase in the 21z SPC SREF SIG TOR ingredients versus previous runs. This tends to run wild during low CAPE/high shear events so to see values this high for an environment like tomorrow is pretty wild.

Keene to Brattleboro 45 huh... damn

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[weatherwiz]

1 minute ago, WxWatcher007 said:

One of my concerns (down in CT) is that we don’t see the discrete cell tornado risk, but rather cells in NY that congeal and bring a straight line risk. 

Agreed. 

Even up north though...the storm mode is going to be key in terms of tornado potential. The 0z HRRR develops alot of activity, so storm mode may get very messy and that will have an impact on updrafts and may add additional challenges for updrafts to really become mature. 

[weatherwiz]

1 minute ago, Prismshine Productions said:

Keene to Brattleboro 45 huh... damn

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Pretty interesting to see that area highlighted...it was an area I had interest in for some of the greatest potential. 

[Quincy]

00z HRRR shows convective inhibition eroding by 18-19z, so you’d expect a bunch of convection to blow up fairly quickly. Leading to messy storm modes. BUT, if a storm or two can thread the needle, or develop out in front, watch out. 

I pulled a few forecast soundings with PDS TOR tags in southern NH as a warm front surges north. Mid level lapse rates are typical New England junk, but with backed low level flow and sizable 0-3km instability, yikes. 

[ineedsnow]

tornado number 3 tomorrow?

[Torch Tiger]

6 minutes ago, ineedsnow said:

tornado number 3 tomorrow?

Hope you see a renegade tor.  I'm not expecting anything more than a shower/t-shower here, but hope others cash in

[Quincy]

I feel like orographic forcing plays more of a role in this region than many other places. You rarely see pronounced EMLs advect into the area when there’s boundary layer instability, so it’s pretty rare that you see 700-500mb lapse rates steeper than 6-6.5 C/km.

The CT River Valley works to channel low level flow a bit, along with instability pooling at lower elevations, and you can see pseudo lee troughs form immediately downwind of the Berkshires. (CAMs hint at this possibly triggering storms tomorrow)

Get 70s dews with backed low level flow, robust southwesterly flow aloft and even modest instability, and that’s enough to do it, assuming you can get discrete storms. I think that’s the biggest wild card here. 

It’s unlikely that we will see a lot of discrete storms, but it only takes one or two to do something quirky. Whether that be interact with a warm front, pre-frontal wind shift or other orographically enhanced mesoscale environment. 

I think we’ve seen several 10% tor threats in the Northeast underperform, but several key ingredients are likely to be in place tomorrow. 

[Prismshine Productions]

Pretty interesting to see that area highlighted...it was an area I had interest in for some of the greatest potential. 

Yeah and I live here...

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[Prismshine Productions]

0z NAM wanted to punt Brattleboro into New Hampshire... PDS TOR

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[weatherwiz]

2 minutes ago, Quincy said:

I feel like orographic forcing plays more of a role in this region than many other places. You rarely see pronounced EMLs advect into the area when there’s boundary layer instability, so it’s pretty rare that you see 700-500mb lapse rates steeper than 6-6.5 C/km.

The CT River Valley works to channel low level flow a bit, along with instability pooling at lower elevations, and you can see pseudo lee troughs form immediately downwind of the Berkshires. (CAMs hint at this possibly triggering storms tomorrow)

Get 70s dews with backed low level flow, robust southwesterly flow aloft and even modest instability, and that’s enough to do it, assuming you can get discrete storms. I think that’s the biggest wild card here. 

It’s unlikely that we will see a lot of discrete storms, but it only takes one or two to do something quirky. Whether that be interact with a warm front, pre-frontal wind shift or other orographically enhanced mesoscale environment. 

I think we’ve seen several 10% tor threats in the Northeast underperform, but several key ingredients are likely to be in place tomorrow. 

Great post. 

I am a bit more uncertain as well as to how much discrete cells we will see tomorrow. I was entertaining the idea yesterday that we could see a line of supercells possibly, but I should have known that was extremely unlikely. 

But to the bolded...that's exactly what I think we'll end up seeing. A few cells that are able to really utilize the environment and produce. Most of the storms may struggle to end up producing. But we'll see what happens...if we get dews 73-76 like the NAM has this makes things a bit more interesting. 

[weatherwiz]

2 minutes ago, Prismshine Productions said:

0z NAM wanted to punt Brattleboro into New Hampshire... PDS TOR

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I'm noticing some of the point-and-click soundings are showing 700-500mb lapse rates around 6.5C/KM but looking at the soundings, those raw numbers don't look right. Not sure that really means anything, I would assume the raw numbers you see in the bottom left box aren't used anywhere (like in the computation of the CAPE). 

[Prismshine Productions]

Close up of the risk zone

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[dendrite]

Goodnight sweet princesses 

[andyhb]

1 minute ago, dendrite said:

Goodnight sweet princesses 

Lapse rates aside (and actually in this particular sounding they aren't that bad), this is impressive.

[Quincy]

Some more maps and both the HRRR and 3km NAM show the secondary Lee trough feature near the CT River Valley, which could, theoretically, trigger discrete storms ahead of the more well-defined trough in eastern NY:

[weatherwiz]

5 minutes ago, andyhb said:

Lapse rates aside (and actually in this particular sounding they aren't that bad), this is impressive.

The NAM/HRRR are spitting out some of the highest supercell/STP values I can remember here. Of course though that doesn’t mean everything, you still need mature enough storms to utilize the environment and that’s the question right now, how many can?

[Torch Tiger]

6c/km or better is fine, given the shear/instability combo.  Of course steep"" 7C up is preferred but also ultra-rare around here, given the other indicies which are mostly higher end

[Quincy]

9 minutes ago, weatherwiz said:

The NAM/HRRR are spitting out some of the highest supercell/STP values I can remember here. Of course though that doesn’t mean everything, you still need mature enough storms to utilize the environment and that’s the question right now, how many can?

By the time the maps show those climatologically insane STP numbers, there will probably be widespread convection already. (21-22z)

Climo favors the 19-20z ish time frame for peak tornado occurrence in central New England, which happens to fit well with tomorrow’s setup.

If something big were to happen, you’d expect it to be around early to afternoon, either near the CT River valley or possibly near the warm front in NH. Later day storms will probably take on more of a clustered/bowing structure mode, but we’ll see. 
 

[RUNNAWAYICEBERG]

Keep that trash far away from here. Experiencing 05/18 is enough for a lifetime. 

[HoarfrostHubb]

28 minutes ago, dendrite said:

Goodnight sweet princesses 

Poor chickens

[Prismshine Productions]

Goodnight sweet princesses 

Wow me and you both had a PDS sounding

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[DavisStraight]

33 minutes ago, weatherwiz said:

The NAM/HRRR are spitting out some of the highest supercell/STP values I can remember here. Of course though that doesn’t mean everything, you still need mature enough storms to utilize the environment and that’s the question right now, how many can?

What's the timing on the storms Wiz? Looks like around dinner time but earlier runs had them much earlier.

[weatherwiz]

Just now, DavisStraight said:

What's the timing on the storms Wiz? 

Could start seeing stuff fire as early as 1-2 PM. Mostly in the 3-8 window though. Another round of isolated storms late evening and early overnight but little svr risk 

[WxWatcher007]

Not surprisingly, the ENH zone was expanded.

 

 

Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0102 AM CDT Sun Jun 23 2024

   Valid 231200Z - 241200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF NEW ENGLAND...

   ...SUMMARY...
   Scattered damaging winds and a few tornadoes are likely across parts
   of the Northeast into the OH/TN valleys, this afternoon and evening.
   Isolated severe storms are also possible over parts of the central
   and northern Plains.

   ...Synopsis...
   Mostly zonal mid-level flow is forecast to remain over the northern
   third of the US as a shortwave trough moves east across parts of WA
   and the southern Canadian Rockies. To the east, a low-amplitude
   shortwave trough embedded within broader zonal flow aloft over the
   Great Lakes and southern Ontario is expected to consolidate and
   strengthen as flow aloft increases over much of New England. A
   secondary trough over the upper MS River Valley is also expected to
   amplify as zonal flow aloft becomes southwesterly over the
   Northeast. Height falls and increasing DPVA will aid in strong
   surface cyclogenesis over the lower St Lawrence Valley. To the east
   of the deepening surface cyclone, a warm front will extend eastward
   across New England to the Atlantic coast, while a cold front and
   surface trough trails toward the southwest into the OH valley.

   ...New England to the Mid Atlantic...
   At the start of the forecast period, scattered thunderstorms are
   likely to be ongoing near the warm front from southern Quebec
   southeastward to southern New England. Insentropic ascent along the
   front from a 30-40 kt LLJ will continue to support scattered storms
   near the frontal zone through the morning hours as rich
   boundary-layer moisture (dewpoints in the upper 60s to low 70s F)
   are advected northward. In the wake of the early morning convection,
   filtered solar heating will allow for moderate destabilization over
   much of New England. Most guidance shows 1500-2000 J/kg of MLCAPE
   developing by early to mid afternoon despite only modest low and
   mid-level lapse rates. More than sufficient for strong updrafts,
   scattered storm development is expected first near the warm front
   and subsequently along the trailing surface trough. Deep-layer shear
   profiles of 45-60 kt support both supercells and short line
   segments. With a favorable parameter space for organized storms,
   damaging winds, isolated hail and a few tornadoes are possible.

   Confidence in a corridor of locally greater severe risk remains
   highest across portions of southern ME, VT, NH and west-central MA.
   Here, area model soundings show large curved hodographs with ESRH of
   250-350 m2/s2 and STP values of 1.5-3, near the climatological
   maximum for the region. With the potential for a mix of supercells
   and line segments, the risk for tornadoes appears somewhat higher.
   Eventual upscale growth into a linear cluster may also support a
   locally greater risk of damaging winds toward the coast later this
   evening. Additional storms are possible as the cold front moves
   through later this evening, though multiple rounds of prior
   convection may limit the severity of any subsequent convection later
   this evening.

[CT Rain]

Not a lot to add here. Looks like there's a bit of a cap south of the Pike which may keep things at bay. Otherwise things look good - especially up north. Some of the forecast hodographs have ~350m2/s2 of 0-1km CAPE which certainly is enough for a significant tornado. 

[ineedsnow]

  LFG 

 ...New England to the Mid Atlantic...
   At the start of the forecast period, scattered thunderstorms are
   likely to be ongoing near the warm front from southern Quebec
   southeastward to southern New England. Insentropic ascent along the
   front from a 30-40 kt LLJ will continue to support scattered storms
   near the frontal zone through the morning hours as rich
   boundary-layer moisture (dewpoints in the upper 60s to low 70s F)
   are advected northward. In the wake of the early morning convection,
   filtered solar heating will allow for moderate destabilization over
   much of New England. Most guidance shows 1500-2000 J/kg of MLCAPE
   developing by early to mid afternoon despite only modest low and
   mid-level lapse rates. More than sufficient for strong updrafts,
   scattered storm development is expected first near the warm front
   and subsequently along the trailing surface trough. Deep-layer shear
   profiles of 45-60 kt support both supercells and short line
   segments. With a favorable parameter space for organized storms,
   damaging winds, isolated hail and a few tornadoes are possible.

   Confidence in a corridor of locally greater severe risk remains
   highest across portions of southern ME, VT, NH and west-central MA.
   Here, area model soundings show large curved hodographs with ESRH of
   250-350 m2/s2 and STP values of 1.5-3, near the climatological
   maximum for the region. With the potential for a mix of supercells
   and line segments, the risk for tornadoes appears somewhat higher.
   Eventual upscale growth into a linear cluster may also support a
   locally greater risk of damaging winds toward the coast later this
   evening. Additional storms are possible as the cold front moves
   through later this evening, though multiple rounds of prior
   convection may limit the severity of any subsequent convection later
   this evening.

[ineedsnow]

 

Given strength of wind field throughout the column, combined with
high instability and steep low level lapse rates, greatest risk is
for strong to damaging winds, with highest probabilities across
western CT, including Hartford county into western and central MA.
In addition, anomalous wind fields thru the column combined with
model soundings showing large curved hodographs and high STP values
of 1.5-3, yielding an elevated risk for tornadoes. CSU machine
learning probs, updraft helocity swaths from the HREF and NCAR wind
probs all support the potential for a high end severe weather event
18z-00z across western-central MA, possibly into northwest CT.
Convection is expected to arrive in RI and eastern MA in a weaken
state, as greatest shear and instability remain northwest of I-95
corridor. Secondary concerns are large hail and brief heavy
downpours.

[CoastalWx]

i thought yesterday maybe this would be more south but central VT to lakes region on east look good.